OPENSSL库的使用-RSA篇

一、RSA算法简介

        RSA公钥加密算法是1977年由Ron Rivest、Adi Shamirh和LenAdleman在（美国麻省理工学院）开发的。RSA取名来自开发他们三者的名字。RSA是目前最有影响力的公钥加密算法，它能够抵抗到目前为止已知的所有密码攻击，已被ISO推荐为公钥数据加密标准。RSA算法基于一个十分简单的数论事实：将两个大素数相乘十分容易，但那时想要对其乘积进行因式分解却极其困难，因此可以将乘积公开作为加密密钥。       RSA公开密钥密码*。所谓的公开密钥密码*就是使用不同的加密密钥与解密密钥，是一种“由已知加密密钥推导出解密密钥在计算上是不可行的”密码*。       RSA算法是一种非对称密码算法，所谓非对称，就是指该算法需要一对密钥，使用其中一个加密，则需要用另一个才能解密。 二、RSA算法加解密用到的函数1、RSA基本结构

struct
     {
      int pad;
      long version;
      const RSA_METHOD *meth;
      ENGINE *engine;
      BIGNUM *n;         n=p*q
      BIGNUM *e;         公开的加密指数，经常为65537（ox10001）
      BIGNUM *d;         私钥
      BIGNUM *p;         大素数p
      BIGNUM *q;         大素数q
      BIGNUM *dmp1;      d mod (p-1)
      BIGNUM *dmq1;      d mod (q-1)
      BIGNUM *iqmp;      (inverse of q) mod p
      int references;
      int flags;
        // ...
      }RSA；

2、初始化函数
RSA * RSA_new(void);初始化一个RSA结构
3、RSA私钥产生函数
RSA *RSA_generate_key(int num, unsigned long e,void (*callback)(int,int,void *), void *cb_arg);产生一个模为num位的密钥对，e为公开的加密指数，一般为65537（0x10001），假如后两个参数不为NULL，将有些调用。在产生密钥对之前，一般需要指定随机数种子 4、判断位数函数
 int RSA_size(const RSA *rsa);返回RSA模的位数，他用来判断需要给加密值分配空间的大小 5、加解密函数1）公钥加密函数int RSA_public_encrypt(int flen, unsigned char *from,unsigned char *to, RSA *rsa, int padding); 2）私钥解密函数int RSA_private_decrypt(int flen, unsigned char *from,unsigned char *to, RSA *rsa, int padding);
3）私钥加密函数int RSA_private_encrypt(int flen, unsigned char *from,unsigned char *to, RSA *rsa,int padding);
4）公钥解密函数int RSA_public_decrypt(int flen, unsigned char *from,unsigned char *to, RSA *rsa,int padding);
flen为要加/解密信息的长度，from为需要加/解密的信息，to为加/解密后的信息，一般to至少要申请 BN_num_bytes(rsa->n)大的空间。加密时Padding表示填充方式，解密时表示去填充方式。
6、 释放函数void RSA_free(RSA *rsa);释放一个RSA结构 7、与字符串处理相关函数BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret);将s中的len位的正整数转化为大数 三、代码示例1、公钥加密

void CPage4::OnButtonPubDecrypt()
{
 // TODO: Add your control notification handler code here
 unsigned char rsaN[1024] = {0};
 unsigned char rsaD[1024] = {0};
 unsigned char rsaE[1024] = {0};
 unsigned char public_e[8] = {0};
 unsigned char publickey_n[1024] = {0};
 unsigned char privatekey_d[1024] = {0};
 unsigned char inputdata[1024] = {0};
 unsigned char output[1024] = {0};
 int e_len = 0;
 int n_len = 0;
 int d_len = 0;
 int inputlen = 0;

 UpdateData(TRUE);

 m_public_e.Remove(' ');
 m_publickey_n.Remove(' ');
 m_privatekey_d.Remove(' ');
 m_inputdata.Remove(' ');

 e_len = m_public_e.GetLength()/2;
    n_len = m_publickey_n.GetLength()/2;
 d_len = m_privatekey_d.GetLength()/2;
 inputlen = m_inputdata.GetLength()/2;

 StrToHex(m_public_e,public_e,e_len);
 StrToHex(m_publickey_n,publickey_n,n_len);
 StrToHex(m_privatekey_d,privatekey_d,d_len);
 StrToHex(m_inputdata,inputdata,inputlen);

 memcpy(rsaN,publickey_n,n_len);
 memcpy(rsaD,privatekey_d,d_len);
 memcpy(rsaE,public_e,e_len);

 RSA* pRsa = RSA_new();

 pRsa->n = BN_bin2bn(rsaN, n_len, NULL);
 pRsa->d = BN_bin2bn(rsaD, d_len, NULL);
 pRsa->e = BN_bin2bn(rsaE, e_len, NULL);

 inputlen=RSA_size(pRsa);

 int ret = RSA_public_encrypt(inputlen,inputdata,output, pRsa, RSA_NO_PADDING);
 if (ret < 0)
 {
  MessageBox("公钥加密失败，请检查输入数据是否正确!");
  RSA_free(pRsa);
  return;
 }

 RSA_free(pRsa);

 HexToStr(output,ret,m_outputdata);

 UpdateData(FALSE);
}

 2、私钥解密

void CPage4::OnButtonPriDecrypt()
{
 // TODO: Add your control notification handler code here
 unsigned char rsaN[1024] = {0};
 unsigned char rsaD[1024] = {0};
 unsigned char rsaE[1024] = {0};
 unsigned char public_e[8] = {0};
 unsigned char publickey_n[1024] = {0};
 unsigned char privatekey_d[1024] = {0};
 unsigned char inputdata[1024] = {0};
 unsigned char output[1024] = {0};
 int e_len = 0;
 int n_len = 0;
 int d_len = 0;
 int inputlen = 0;

 UpdateData(TRUE);

 m_public_e.Remove(' ');
 m_publickey_n.Remove(' ');
 m_privatekey_d.Remove(' ');
 m_inputdata.Remove(' ');

 e_len = m_public_e.GetLength()/2;
    n_len = m_publickey_n.GetLength()/2;
 d_len = m_privatekey_d.GetLength()/2;
 inputlen = m_inputdata.GetLength()/2;

 StrToHex(m_public_e,public_e,e_len);
 StrToHex(m_publickey_n,publickey_n,n_len);
 StrToHex(m_privatekey_d,privatekey_d,d_len);
 StrToHex(m_inputdata,inputdata,inputlen);

 memcpy(rsaN,publickey_n,n_len);
 memcpy(rsaD,privatekey_d,d_len);
 memcpy(rsaE,public_e,e_len);

 RSA* pRsa = RSA_new();
 pRsa->n = BN_bin2bn(rsaN, n_len, NULL);
 pRsa->d = BN_bin2bn(rsaD, d_len, NULL);
 pRsa->e = BN_bin2bn(rsaE, e_len, NULL);

 //inputlen=RSA_size(pRsa)-11;

 int ret = RSA_private_decrypt(inputlen,inputdata,output, pRsa, RSA_NO_PADDING);
 if (ret < 0)
 {
  MessageBox("私钥解密失败，请检查输入数据是否正确!");
  RSA_free(pRsa);
  return;
 }

 RSA_free(pRsa);

 HexToStr(output,ret,m_outputdata);

 UpdateData(FALSE);
}

 3、私钥加密

void CPage4::OnButtonEncrypt()
{
 // TODO: Add your control notification handler code here
 unsigned char rsaN[1024] = {0};
 unsigned char rsaD[1024] = {0};
 unsigned char rsaE[1024] = {0};
 unsigned char public_e[8] = {0};
 unsigned char publickey_n[1024] = {0};
 unsigned char privatekey_d[1024] = {0};
 unsigned char inputdata[1024] = {0};
 unsigned char output[1024] = {0};
 int e_len = 0;
 int n_len = 0;
 int d_len = 0;
 int inputlen = 0;

 UpdateData(TRUE);

 m_public_e.Remove(' ');
 m_publickey_n.Remove(' ');
 m_privatekey_d.Remove(' ');
 m_inputdata.Remove(' ');

 e_len = m_public_e.GetLength()/2;
    n_len = m_publickey_n.GetLength()/2;
 d_len = m_privatekey_d.GetLength()/2;
 inputlen = m_inputdata.GetLength()/2;

 StrToHex(m_public_e,public_e,e_len);
 StrToHex(m_publickey_n,publickey_n,n_len);
 StrToHex(m_privatekey_d,privatekey_d,d_len);
 StrToHex(m_inputdata,inputdata,inputlen);

 memcpy(rsaN,publickey_n,n_len);
 memcpy(rsaD,privatekey_d,d_len);
 memcpy(rsaE,public_e,e_len);

 RSA* pRsa = RSA_new();
 pRsa->n = BN_bin2bn(rsaN, n_len, NULL);
 pRsa->d = BN_bin2bn(rsaD, d_len, NULL);
 pRsa->e = BN_bin2bn(rsaE, e_len, NULL);

 inputlen=RSA_size(pRsa);

 int ret = RSA_private_encrypt(inputlen,inputdata,output, pRsa, RSA_NO_PADDING);
 if (ret < 0)
 {
  MessageBox("私钥加密失败，请检查输入数据是否正确!");
  RSA_free(pRsa);
  return;
 }

 RSA_free(pRsa);

 HexToStr(output,ret,m_outputdata);

 UpdateData(FALSE);

}

 

4、公钥解密

void CPage4::OnButtonDecrypt()
{
 // TODO: Add your control notification handler code here
 unsigned char rsaN[1024] = {0};
 unsigned char rsaD[1024] = {0};
 unsigned char rsaE[1024] = {0};
 unsigned char public_e[8] = {0};
 unsigned char publickey_n[1024] = {0};
 unsigned char privatekey_d[1024] = {0};
 unsigned char inputdata[1024] = {0};
 unsigned char output[1024] = {0};
 int e_len = 0;
 int n_len = 0;
 int d_len = 0;
 int inputlen = 0;

 UpdateData(TRUE);

 m_public_e.Remove(' ');
 m_publickey_n.Remove(' ');
 m_privatekey_d.Remove(' ');
 m_inputdata.Remove(' ');

 e_len = m_public_e.GetLength()/2;
    n_len = m_publickey_n.GetLength()/2;
 d_len = m_privatekey_d.GetLength()/2;
 inputlen = m_inputdata.GetLength()/2;

 StrToHex(m_public_e,public_e,e_len);
 StrToHex(m_publickey_n,publickey_n,n_len);
 StrToHex(m_privatekey_d,privatekey_d,d_len);
 StrToHex(m_inputdata,inputdata,inputlen);

 memcpy(rsaN,publickey_n,n_len);
 memcpy(rsaD,privatekey_d,d_len);
 memcpy(rsaE,public_e,e_len);

 RSA* pRsa = RSA_new();
 pRsa->n = BN_bin2bn(rsaN, n_len, NULL);
 pRsa->d = BN_bin2bn(rsaD, d_len, NULL);
 pRsa->e = BN_bin2bn(rsaE, e_len, NULL);

 //inputlen=RSA_size(pRsa)-11;

 int ret = RSA_public_decrypt(inputlen,inputdata,output, pRsa, RSA_NO_PADDING);
 if (ret < 0)
 {
  MessageBox("公钥解密失败，请检查输入数据是否正确!");
  RSA_free(pRsa);
  return;
 }

 RSA_free(pRsa);

 HexToStr(output,ret,m_outputdata);

 UpdateData(FALSE);
}

 
5、产生RSA密钥对

void CPage4::OnButtonRsa()
{
 // TODO: Add your control notification handler code here
 RSA* key;
 unsigned char rsa_n[1024];
 unsigned char rsa_d[1024];
 char keylen[10];
 int len;

 UpdateData(TRUE);

 strcpy(keylen,m_keylen);
 len = atoi(keylen);

 key = RSA_new();

 key = RSA_generate_key(len,0x10001,NULL,NULL);

 BN_bn2bin(key->n,rsa_n ); // 保存公钥
 BN_bn2bin(key->d,rsa_d ); // 保存私钥

 RSA_free(key);

 HexToStr(rsa_n,len/8,m_publickey_n);
 HexToStr(rsa_d,len/8,m_privatekey_d);

 UpdateData(FALSE);

}